Drilling work devices are known which include a drive system that makes a workpiece and a tool (drill, for example) execute relative rotating motion and feeding motion in order to form a hole in the workpiece (refer to Patent Literatures 1 to 5, for example).
When a hole is formed in a workpiece by such a drilling work device, from a viewpoint of improving working accuracy and working efficiency or protecting a cutting tool, according to the quality of material of the workpiece and the depth of the hole, working conditions including the spindle speed of the rotating motion or the feeding speed of the feeding motion between the workpiece and the tool are patterned and set beforehand (refer to Patent Literature 2, for example), and are set according to the load torque applied to a tool during drilling work (refer to Patent Literatures 3 to 5, for example). Also, in order to form a deep hole, step feed working may be executed in which after a tool is retracted tentatively to discharge cutting chips, the tool is advanced again (Patent Literatures 2, 3, for example).